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Homework Help: Energy and temperature

  1. Jul 18, 2009 #1
    1. The problem statement, all variables and given/known data

    A 5-g coin is dropped from a 300-m building. If it reaches a terminal velocity of 45 m/s, and the rest of the energy is converted to heating the coin, what is the change in temperature (in °C) of the coin? (The specific heat of copper is 387 J/kg °C.)

    I have no idea how to start the problem..
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  3. Jul 18, 2009 #2


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    Think about conservation of energy.
  4. Jul 18, 2009 #3
    Potential Energy initial = delta Q?

    I don't have a physics book and the teacher pdf notes kinda suck can i get the formula for the thermal change in energy
  5. Jul 18, 2009 #4


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    Nope. Not all of it is converted into heat. Obviously if the object starts at 0 m/s and ends up at 45 m/s, it has gained some kinetic energy too.
  6. Jul 18, 2009 #5
    mgd= delta q + KE?
  7. Jul 18, 2009 #6
    Total energy before the coin is dropped = total energy after it reaches terminal velocity
    What is/are the energy/energies present before it is dropped?
    What is/are the energy/energies present after it reaches terminal velocity?
  8. Jul 18, 2009 #7
    Sorry i'm late....
    the last one is right
  9. Jul 18, 2009 #8


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  10. Jul 18, 2009 #9
    (.005)(9.8)(300) = (5)(387)T + (.5)(.005)(45^2)

    So t = 4.98
    does that look right?
  11. Jul 18, 2009 #10
    my other question is if i did it like that wouldn't the units for my answer be 4.98 kg/J = delta T ??
  12. Jul 18, 2009 #11
    the number is right but not the unit. What is the unit for temperature?
  13. Jul 18, 2009 #12
    o0o got it C the kg and J cancels out
  14. Jul 18, 2009 #13
    thanks for all the help
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